Wave speed equals frequency multiplied by wavelength
Обяснение
The wave-speed relation is v = fbb, so speed is the product of frequency and wavelength. The other options rearrange the relation incorrectly.
The wavelength decreases so that v remains constant
Обяснение
With v fixed, increasing f must reduce bb so that v = fbb still holds. This is the standard frequency-wavelength trade-off in the same medium.
Its frequency
Обяснение
Reflection preserves the wave frequency. The direction changes, but the reflected wave keeps the same frequency as the incident wave.
The wavefronts bend because the propagation speed changes
Обяснение
Refraction is caused by a change in speed across the boundary, which bends the wavefronts. Frequency is not the defining change here.
A ray aimed through the optical center
Обяснение
A ray through the optical center continues straight in the thin-lens approximation. The parallel and focus rays obey different principal-ray rules.
The image distance from the object distance and focal length
Обяснение
The thin-lens equation links object distance, image distance, and focal length. It is used with magnification to predict image formation.
A range of electromagnetic radiation types ordered by frequency and wavelength
Обяснение
The electromagnetic spectrum includes all electromagnetic radiation types arranged by frequency and wavelength. Visible light is only a small part of it.
Cosmological red-shift in line spectra
Обяснение
Cosmological red-shift in spectra supports the idea that distant galaxies are moving away, consistent with expansion. The other choices are unrelated to cosmological expansion.
The Sun
Обяснение
In the heliocentric model, the Sun is at the center and the planets orbit it. This contrasts with Earth-centered models.
Mass
Обяснение
Mass is the key factor controlling stellar evolution and the star's end state. The other options do not determine the evolution path in the same way.
Complete reflection at a boundary when the incidence angle exceeds the critical angle
Обяснение
Total internal reflection occurs when the incidence angle is greater than the critical angle, so the wave is completely reflected. It is not the same as ordinary refraction.
An endoscope
Обяснение
An endoscope uses fibre optics to transmit light and image information inside the body. A prismatic periscope and a magnifying glass serve different purposes.
Force multiplied by the time interval
Обяснение
Impulse is the effect of a force acting over time, and it equals the change in momentum. This is why force over a longer time can change momentum in the same way with a smaller peak force.
Mass times velocity
Обяснение
Momentum is defined as p = mv. The force-time product is impulse, not momentum.
Iron, nickel, and cobalt
Обяснение
The three ferromagnetic elements named are iron, nickel, and cobalt. The other groups are not the standard ferromagnetic set here.
The direction of force on a north-seeking pole
Обяснение
Magnetic field lines show the field direction, taken as the direction of force on a north pole, and their spacing indicates relative strength. They are not physical paths traveled by current.
The same current flows through each component
Обяснение
In a series circuit, the same current passes through every component. Equal voltage across components is a property of parallel connections.
The RMS value
Обяснение
The stated 230 V AC is the RMS value, the effective voltage used for power comparisons. It is related to the peak value by V_rms = V_peak / 2.
Запомнете отговорите с 18 флашкарти по Fundamentals of Wave Optics and Cosmology.
Travelling wave — definition?
A disturbance propagating energy without matter transport.
Wave speed relation?
v = f λ, relates speed, frequency, wavelength.
Transverse wave — displacement?
Displacement is perpendicular to propagation direction.
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